Cyberjutsu

26 Shinobi Tradecraft Secret techniques to infiltrate without fail are deceptive, and they are varied and flexible and are done according to opportunity. Thus, as a basis, you should embrace the old ways of the shinobi who served under ancient great generals, but remember not only to keep to these ways but to adapt them, each dependent on the situation and the moment.

Even if there is a din outside, be aware that the guardhouse should not be left completely empty. Also, you should listen for any sounds.

—Yoshimori Hyakushu #66

While shinobi were sometimes hired to guard castles and other fortifications (as described in Shōninki ¹), non-shinobi soldiers or mercenaries—warriors trained to repel common invaders—occupied most guard stations ...